/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.jackrabbit.webdav.version.report;

import java.util.HashSet;

import javax.servlet.http.HttpServletResponse;

import org.apache.jackrabbit.webdav.DavConstants;
import org.apache.jackrabbit.webdav.DavException;
import org.apache.jackrabbit.webdav.DavResource;
import org.apache.jackrabbit.webdav.DavResourceIterator;
import org.apache.jackrabbit.webdav.MultiStatus;
import org.apache.jackrabbit.webdav.property.DavPropertyNameSet;
import org.apache.jackrabbit.webdav.version.DeltaVConstants;
import org.apache.jackrabbit.webdav.version.VersionControlledResource;
import org.apache.jackrabbit.webdav.version.VersionHistoryResource;
import org.apache.jackrabbit.webdav.xml.DomUtil;
import org.apache.jackrabbit.webdav.xml.ElementIterator;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Element;

/**
 * <code>LocateByHistoryReport</code> encapsulates the DAV:locate-by-hisotry
 * report, that may be used to locate a version-controlled resource for that
 * version history. The DAV:locate-by-history report can be applied to a
 * collection to locate the collection member that is a version-controlled
 * resource for a specified version history resource.
 * 
 * <pre>
 * &lt;!ELEMENT locate-by-history (version-history-set, prop)&gt;
 * &lt;!ELEMENT version-history-set (href+)&gt;
 * </pre>
 */
public class LocateByHistoryReport implements Report, DeltaVConstants {

	private static Logger log = LoggerFactory
			.getLogger(LocateByHistoryReport.class);

	private ReportInfo info;
	private HashSet<String> vhHrefSet = new HashSet<String>();
	private DavResource resource;

	/**
	 * Fill the <code>MultiStatus</code> with the
	 * <code>MultiStatusResponses</code> generated for the specified resource
	 * and its members according to the depth value.
	 * 
	 * @param res
	 * @param propNameSet
	 * @param depth
	 * @param ms
	 */
	private void buildResponse(DavResource res, DavPropertyNameSet propNameSet,
			int depth, MultiStatus ms) {
		// loop over members first, since this report only list members
		DavResourceIterator it = res.getMembers();
		while (!vhHrefSet.isEmpty() && it.hasNext()) {
			DavResource childRes = it.nextResource();
			if (childRes instanceof VersionControlledResource) {
				try {
					VersionHistoryResource vhr = ((VersionControlledResource) childRes)
							.getVersionHistory();
					if (vhHrefSet.remove(vhr.getHref())) {
						if (propNameSet.isEmpty()) {
							ms.addResourceStatus(childRes,
									HttpServletResponse.SC_OK, 0);
						} else {
							ms.addResourceProperties(childRes, propNameSet, 0);
						}
					}
				} catch (DavException e) {
					log.info(e.getMessage());
				}
			}
			// traverse subtree
			if (depth > 0) {
				buildResponse(it.nextResource(), propNameSet, depth - 1, ms);
			}
		}
	}

	/**
	 * Retrieve the <code>MultiStatus</code> that is returned in response to a
	 * locate-by-history report request.
	 * 
	 * @return
	 * @throws NullPointerException
	 *             if info or resource is <code>null</code>.
	 */
	private MultiStatus getMultiStatus() {
		MultiStatus ms = new MultiStatus();
		buildResponse(resource, info.getPropertyNameSet(), info.getDepth(), ms);
		return ms;
	}

	/**
	 * Returns {@link ReportType#LOCATE_BY_HISTORY}.
	 * 
	 * @see Report#getType()
	 */
	public ReportType getType() {
		return ReportType.LOCATE_BY_HISTORY;
	}

	/**
	 * @see Report#init(DavResource, ReportInfo)
	 */
	public void init(DavResource resource, ReportInfo info) throws DavException {
		if (resource == null
				|| !(resource instanceof VersionControlledResource)) {
			throw new DavException(
					HttpServletResponse.SC_BAD_REQUEST,
					"DAV:version-tree report can only be created for version-controlled resources and version resources.");
		}
		this.resource = resource;
		setInfo(info);
	}

	/**
	 * Always returns <code>true</code>.
	 * 
	 * @return true
	 * @see org.apache.jackrabbit.webdav.version.report.Report#isMultiStatusReport()
	 */
	public boolean isMultiStatusReport() {
		return true;
	}

	/**
	 * Set the <code>ReportInfo</code>
	 * 
	 * @param info
	 * @throws DavException
	 *             if the given <code>ReportInfo</code> does not contain a
	 *             DAV:version-tree element.
	 */
	private void setInfo(ReportInfo info) throws DavException {
		if (info == null || !getType().isRequestedReportType(info)) {
			throw new DavException(HttpServletResponse.SC_BAD_REQUEST,
					"DAV:locate-by-history element expected.");
		}
		Element versionHistorySet = info.getContentElement(
				XML_VERSION_HISTORY_SET, NAMESPACE);
		if (versionHistorySet == null) {
			throw new DavException(
					HttpServletResponse.SC_BAD_REQUEST,
					"The DAV:locate-by-history element must contain a DAV:version-history-set child.");
		}
		ElementIterator it = DomUtil.getChildren(versionHistorySet,
				DavConstants.XML_HREF, DavConstants.NAMESPACE);
		while (it.hasNext()) {
			String href = DomUtil.getText(it.nextElement());
			if (href != null) {
				vhHrefSet.add(href);
			}
		}
		this.info = info;
	}

	/**
	 * Run the report.
	 * 
	 * @return Xml <code>Document</code> representing the report in the required
	 *         format.
	 * @see org.apache.jackrabbit.webdav.xml.XmlSerializable#toXml(Document)
	 * @param document
	 */
	public Element toXml(Document document) {
		return getMultiStatus().toXml(document);
	}
}